d4.06.40 An example of a distributed matrix for PETSc

Summary:

To use the solvers from the PETSc library in parallel, you must provide an assembled matrix distributed across the available processors according to a distribution model imposed by PETSc (distribution by group of contiguous rows). The Code_Aster data distribution model is based on a distribution of meshes between processors. It leads to an assembled matrix that does not follow the PETSc distribution model. We explain here using a simple physical example the different numberings of the degrees of freedom: local and global numbering for Code_Aster then numbering PETSc.

• 1. Introduction
• 2. Model problem
  • 2.1. Geometry
  • 2.2. Material properties
  • 2.3. 2D modeling
  • 2.4. Limit conditions and loading
  • 2.5. Distribution of the problem
• 3. Overview of the linear system
  • 3.1. Ongoing problem
  • 3.2. Numbering the equations of the global Code_Aster matrix
  • 3.3. Numbering the equations of the local Aster matrix
• 4. The linear system for modeling A
  • 4.1. The discrete system
  • 4.2. The descriptors of the matrix
• 5. The linear system for B modeling
  • 5.1. The discrete system
  • 5.2. The descriptors of the assembled matrix
• 6. Building the PETSc matrix
  • 6.1. Data model PETSc
  • 6.2. Matrix descriptor for B modeling